The wafer-level package technology is a technology that collectively seals a number of elements formed on a semiconductor wafer before partitioning the semiconductor wafer into individual chips, and is widely used for manufacturing small semiconductor devices because the cost is low and it can form electronic elements with their respective sizes.
On the other hand, attempts have been made recently for collectively forming electronic devices on a wafer that have movable parts such as switches, variable-capacitance capacitors, crystal oscillators, and the like. Thereupon, there has been demand for the wafer-level package technology to be used for sealing these electronic devices to make the electronic devices smaller and to reduce the manufacturing cost.
For example, if an electronic device has a movable part, and an element corresponding to the electronic device formed on a wafer is to be sealed on the wafer, it is desirable that the element be covered by a cover member on the wafer so that a space is partitioned around the element by the cover member on the wafer.
For example, Patent Document 1 discloses a method of sealing an element by forming an element at a concave part on a surface of a wafer, and bonding a cover member to the surface of the wafer by a wax material so that the element is sealed. Also, in Patent Document 2, a cover member is bonded by a wax material layer to an upper surface of a sidewall member forming the circumference that is formed to surround an element on a wafer so that the element is sealed.
When a cover member is bonded by a wax material layer to a surface or an upper surface of an external sidewall member on the surface of a wafer as described above, the wax material layer needs to be melted, and it is preferable to press the cover member lightly so that the melted wax material layer levels out concavities and convexities on the surface of the substrate and the surface of the cover member to obtain secure sealing. However, there is a risk in applying pressure to the melted wax material layer that the wax material is flowed out or pushed out into the space around the element. If the flowed-out wax material contacts the element, it not only entails an electrical defect, but also hinders operation of a movable part of the element if there are any.
Thereupon, considering such inflowing of a wax material, the dimensions of the space are set larger than required conventionally, which makes the dimensions of the electronic device increase.